Apparatus and method for fabrication of three dimensional objects

ABSTRACT

digital fabrication apparatus of large built-volume three-dimensional (3D) objects.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a DIVISIONAL Non-Provisional Utility Applicationthat claims the benefit of priority of the co-pending U.S.Non-provisional Utility application Ser. No. 15/499,891 with filing date28 Apr. 2017, which claims the benefit of priority of U.S. ProvisionalUtility Patent Application 62/329,177 with a filing date 28 Apr. 2016,the entire disclosures of all of which applications are expresslyincorporated by reference in their entirety herein.

All documents mentioned in this specification are herein incorporated byreference to the same extent as if each individual document wasspecifically and individually indicated to be incorporated by reference.

It should be noted that throughout the disclosure, where, a definitionor use of a term in any incorporated documents) is inconsistent orcontrary to the definition of that term provided herein, the definitionof that term provided herein applies and the definition of that term inthe incorporated document(s) does not apply.

BACKGROUND OF THE INVENTION Field of the Invention

One or more embodiments of the present invention are related, toapparatus and method for fabrication, manipulation, or modification oflarge built-volume three-dimensional (3D) objects.

Description of Related Art

Conventional 3D printers are well known and have been in use for anumber of years. Regrettably, most conventional small sized entry-level3D printers are designed for an average approximate built-volume ofabout 6″×6″×6″. Unfortunately, conventional small sized entry-level 3Dprinters use conventional subsystems and components (e.g., frame, drivesystems, heating systems, power requirements, control systems, etc.)that are specifically designed for smaller sized built-volumes and notsuited for and in fact, not even scalable for larger built-volumefabrications. For example, conventional small sized entry-level 3Dprinters use a toothed belt drive system for moving a printer-head shortdistances, but toothed belt drive systems are not suited, for actuationand correct positioning of the printer-head at long travel distances dueto greater degree of belt-play such as belt-whip or belt-lag caused bylonger drive belts. In fact, belt drive systems in general are not wellsuited for correct positioning of a print head whether for short or longtravel distances.

Unfortunately, today's so-called “larger” 3D printers (averageapproximate built-volume of about 18″×18″×8″), use technologies that arebased on traditional Computer Numerical Control (CNC) machines, whichare very costly. CNC machines are engineered to apply and to withstandlarge forces required for a tool that must contact and remove, materialfrom a workpiece by cutting, carving, machining, drilling, grinding,milling, etc. Given the large forces required, CNC, machines use complexclosed-loop control systems for correctly moving and positioning thetool so that it does not “crash” into the workpiece, causingcatastrophic damage to the workpiece and possibly to the CNC machineitself.

Further, conventional 3D printers based on traditional CNC machinestechnologies require the use of proprietary software that recognizeproprietary packaged filament materials (“printer cartridge” orcanister) used for fabrication of 3D objects. Accordingly, as withinkjet printers, consumers are locked into specific venders forpurchasing proprietary packaged filament materials for fabricating theirproducts when using 3D printers based on CNC machine technologies.

Accordingly, in light of the current state of the art and the drawbacksto 3D printers mentioned above, a need exists for an apparatus and amethod for fabrication, manipulation, and modification ofthree-dimensional objects that would allow scalable for largebuilt-volumes, but without reliance on costly CNC machine basedtechnologies.

BRIEF SUMMARY OF THE INVENTION

A non-limiting, exemplary aspect of an embodiment of the presentinvention provides digital fabrication apparatus, comprising:

a frame having a frame longitudinal axis and a frame transverse axis;

first frame members that are parallel the frame longitudinal axis,forming vertically oriented frame members that form the sides of theframe;

second frame members that are parallel the frame transverse axis,forming horizontally oriented frame members;

wherein: combination of vertically oriented frame members andhorizontally oriented frame members sectionalize the frame, formingframe sections.

These and other features and aspects of the invention will be apparentto those skilled in the art from the following detailed description ofpreferred non-limiting exemplary embodiments, taken together with thedrawings and the claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

It is to be understood that the drawings are to be used for the purposesof exemplary illustration only and not as a definition of the limits ofthe invention. Throughout the disclosure, the word “exemplary” may beused to mean “serving as an example, instance, or illustration,” but theabsence of the term “exemplary” does not denote a limiting embodiment.Any embodiment described as “exemplary” is not necessarily to beconstrued as preferred or advantageous over other embodiments. In thedrawings, like reference character(s) present corresponding part(s)throughout.

FIGS. 1A to 1C are non-limiting overview illustrations of a digitalfabrication apparatus for fabrication of 3D workpiece in accordance withone or more embodiments of the present invention;

FIGS. 2A and 2B are non-limiting exemplary illustrations of anon-limiting frame construct of the digital fabrication apparatus shownin FIGS. 1A to 1C in accordance with one or, more embodiments of thepresent invention;

FIGS. 3A to 3D are non-limiting, exemplary illustrations of a lower (orfirst) section of the digital fabrication apparatus shown in FIGS. 1A to2B in accordance with one or more embodiments of the present invention;

FIGS. 4A to 4H are non-limiting, exemplary illustrations of a floorplate assembly of the digital fabrication apparatus shown in FIGS. 1A to3D in accordance with one or more embodiments of the present invention;

FIGS. 5A to 5O are non-limiting, exemplary illustrations of a workpieceplatform assembly of the digital fabrication apparatus shown in FIGS. 1Ato 4H in accordance with one or more embodiments of the presentinvention;

FIGS. 6A to 6P-4 are non-limiting, exemplary illustrations ofpositioning system of the digital fabrication apparatus shown in FIGS.1A to 5O in accordance with one or more embodiments of the presentinvention;

FIGS. 7A to 7L are non-limiting, exemplary illustrations of X-directionmotive force mechanisms and Y-direction motive force mechanisms of thedigital fabrication apparatus shown in FIGS. 1A to 6P-4 in accordancewith one or more embodiments of the present invention;

FIGS. 8A to 8I are non-limiting, exemplary illustrations of a moveablefabrication tool of the digital fabrication apparatus shown in FIGS. 1Ato 7L in accordance with one or more embodiments of the presentinvention; and

FIGS. 9A to 9N are non-limiting, exemplary illustrations of a top plateand Z-direction motive force mechanisms of the digital fabricationapparatus shown in FIGS. 1A to 8I in accordance with one or moreembodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of presently preferred embodimentsof the invention and is not intended to represent the only forms inwhich the present invention may be constructed and or utilized.

It is to be appreciated that certain features of the invention, whichare, for clarity, described in the context of separate embodiments, mayalso be provided in combination in a single embodiment. Conversely,various features of the invention that are, for brevity, described inthe context of a single embodiment may also be provided separately or inany suitable sub-combination or as suitable in any other describedembodiment of the invention. Stated otherwise, although the invention isdescribed below in terms of various exemplary embodiments andimplementations, it should be understood that the various features andaspects described in one or more of the individual embodiments are notlimited in their applicability to the particular embodiment with whichthey are described, but instead can be applied, alone or in variouscombinations, to one or more of the other embodiments of the invention.

Throughout the disclosure, references to a three dimensional (3D)printer are meant as illustrative, convenience of example, and fordiscussion purposes only. That is, the applications of the presentinvention should not be limited to (3D) printers but may also be used(without much modifications, if any) for other purposes that may requirea defined two- or three-dimensional path. Non-limiting, non-exhaustivelisting of examples of other applications may include, for example,laser etching or marking or cutting, part measurement for reverseengineering purposes using various metrology tools, the 3D scanning ofcomponents using 3D scanners, or light to medium duty machiningprocesses such as routing, drilling, or the application of sprayedmaterials such as paint, or the mounting of remotely controllable cameraor video equipment to support for instance, process analysis or thedevelopment of training materials.

For the purposes of the present invention, the use of the termsfabricate (or its derivatives thereof such as fabrication) and create,manufacture, produce, construct, build, form, or fashion are equivalentand interchangeable.

The term coordinate may refer to each of a group of numbers used toindicate the position of a point in three-dimensional space.

As indicated above, CNC machine technology is costly. The presentinvention has recognized that 3D printers do not remove material from aworkpiece for fabrication of a product. Further, 3D printers do not havea tool to physically contact, a workpiece at a required minimum force toremove materials from the workpiece for fabrication of a product.

The tool for fabrication of a product using a 3D printer adds orbuilds-up material layers for fabrication of a product and hence, doesnot need or require application of or resistance to large forces neededfor removing material from the workpiece as is required by CNC machine.Accordingly, the present invention has recognized that the generaloperational principle of a 3D printer in fabrication of a desiredproduct is the opposite of that of a CNC machine. Therefore, applicationof CNC machine technology is not appropriately suited in 3D printingenvironment, which is the reason for costly “large” size printers basedon CNC machine technologies.

A 3D printer fabricates products based on build-up of material layerswhereas a CNC machine fabricates products based on removal of materialfrom an existing workpiece, requiring large forces for the CNC tool.Accordingly, one or more embodiments of the present invention provide anapparatus and a method for fabrication of three-dimensional objectswithout using CNC machine technologies (if any) to reduce costs withoutsacrifice in correct positioning of a moveable fabrication tool such asa “print head” at a desired location within a three-dimensional space.

As detailed below, an important aspect in providing the capability tocorrectly position a moveable fabrication tool at a desired locationwithin a very large three-dimensional (3D) space for a largebuild-volume (e.g., 80″×80″×80″) that may also be scalable (without muchmodifications, if any) to even a larger 3D build-volume at very low costis to provide an apparatus that has an extremely accurate build rigidframe at low cost.

As further detailed below, another important aspect in providing thecapability to correctly position the moveable fabrication tool a largebuild-volume workpiece is to provide the flexibility in terms oftolerances needed to compensate for inherent operational variations ofvarious components.

FIGS. 1A to 1C are non-limiting overview illustrations of a digitalfabrication apparatus for fabrication of 3D workpiece in accordance withone or more embodiments of the present invention. As illustrated,digital fabrication apparatus 100 includes a large 3D space 102 for alarge build-volume of about 80″×80″×80″.

As further detailed below, digital fabrication apparatus 100 may, begenerally described as having a lower or first section 104 for storageof components, a generally middle or second section 106 that defines thework-space for fabricating a 3D workpiece, and a top or third section108 that houses various other components, including some of thecomponents that constitute the Z-direction motive force mechanisms.

The entire digital fabrication apparatus 100 may be mounted on a set ofwheels 110 (FIG. 1B), with corner ends 112 cut out to provide clearancefor free movement of wheels 110 and to prevent sharp ends of digitalfabrication apparatus 100 from being cut onto objects. Digitalfabrication apparatus 100 further includes a conventional externalmonitor 114 for visual interface between users and conventional computersoftware that controls digital fabrication apparatus 100 and controlpanel with LCD display 116 for manual control of a moveable fabricationtool 118 (best shown in FIG. 4A).

As best illustrated in FIGS. 1A and 1C, second section 106 includesremovable window panels 120 on all four sides that move (slide laterallyby rollers) along a reciprocating path from a fully closed to a fullyopen position on window sill rails 122 and window header rails 124.Removable window panels 120 are preferably maximized in term of theirsize (over 3 or 4 feet in height and as wide as allowed by a frame 126of digital fabrication apparatus 100) to enable full access to secondsection 106.

Maximum access to second section 106 allows for easy initialization andsetup of digital fabrication apparatus 100 as well as easy removal ofthe fabricated piece (which has a large built-volume). An importantaspect for providing removable window panels 120 and actually closingoff the middle section 106 during operation of fabrication of an objectis to provide a fully closed, controlled environment (in terms oftemperature, humidity, etc.) within which a product is fabricated.

As best illustrated in FIGS. 1C (and 2A) and, further detailed below,one or more embodiment of the present invention provide a digitalfabrication apparatus 100 that is comprised of frame 126 having a framelongitudinal axis 130 and a frame transverse axis 132. Frame 126 iscomprised of first frame members that are parallel frame longitudinalaxis 130, forming vertically oriented frame members that form the sides134 of frame 126. Frame further includes second frame members that areparallel frame transverse axis 132, forming horizontally oriented framemembers 136. A combination of vertically oriented frame members 134 andhorizontally oriented frame members 136 sectionalize frame 126, formingthe above described sections.

As indicated above, extremely accurate build rigid frame is oneimportant factor in providing the capability to correctly positionmoveable fabrication tool 118. FIGS. 2A and 2B are non-limitingexemplary illustrations of a non-limiting frame construct of the digitalfabrication apparatus shown in FIGS. 1A to 1C in accordance with one ormore embodiments of the present invention. As illustrated in FIGS. 2Aand 2B, frame 126 of digital fabrication apparatus 100 is comprised ofwell-known tab-slot construction, which provides a very sturdy frame 126for large moving components, associated with moveable fabrication tool118.

As illustrated, a vertically oriented frame member 134 is comprised offrame connection openings or slots 138 that receive frame connectionflanges or tabs 140 of both horizontally oriented frame members 136 andadjacent vertically oriented frame members 134, where tabs 140 aremechanically connected (e.g., welded) within slots 138 of verticallyoriented frame member 134. It should be emphasized that verticallyoriented frame members 134 are connected to other vertically orientedframe members by the same tab/slot connectivity.

As best illustrated in FIG. 2B, frame connection flanges 140 extend fromperiphery sides of frame members (horizontal or vertical). Frameconnection flanges 140 include lateral beveled (or tapered surfaces or)edges 142 that form chamfered sides that facilitate easy insertion oftabs into slots 138. Chamfered sides 142 lead to lateral reliefs 144(rounded recesses) that receive vertical sides of slots 138 of the framemembers.

FIGS. 3A to 3D are non-limiting, exemplary illustrations of a lower (orfirst) section of the digital fabrication apparatus shown in FIGS. 1A to2B in accordance with one or, more embodiments of the present invention.As illustrated, first or lower section 104 of digital fabricationapparatus 100 is enclosed by one or more removable access panel 146,forming a storage space 148 having sufficient height for housingoperational and support equipment (detailed below).

First frame section 104 further includes a first horizontally orientedframe member 134 as a bottom frame plate 150 that is mechanicallyconnected to the vertically oriented frame members 134 with tab/slotconnectivity, as described above. Bottom frame plate 150 includes a setof fastener openings 152 for securing one or more operational andsupport equipment to bottom frame plate 150 by fasteners, belts, etc.

FIG. 3C is a non-limiting, exemplary illustration of a lower sectionwith access panels removed and operational and support equipment pulledout and shown in accordance with one or more embodiments of the presentinvention. FIG. 3D is a non-limiting, exemplary schematic illustrationof one or more operational and support equipment of the digitalfabrication apparatus in accordance with one or more embodiments of thepresent invention.

As illustrated in FIGS. 3C and 3D, digital fabrication apparatus 100includes electrical circuits (equipment, components, or systems) thatare isolated into groups, with each electrically isolated group ofcircuits separately and individually powered by a correspondinglycommensurate individual, separate, and isolated power supply 154 whereinN individual, separate, and isolated power supplies are used to power acorresponding number of N sets of isolated circuits. Isolating circuitsinto individually isolated group of equipment by using N sets of powersupplies for N sets of circuits (equipment) provides convenience interms of design, simplified maintainability, and redundancy. That is,each set of equipment with their own set of power requirement aregrouped and powered by their respective power supply at their respectiverequired power, making the power design simple. Further, maintainabilityis also simplified in that if a component is required to be maintained,all systems (which are isolated) need not be shut-down, only thespecified power supply for the specified equipment is shut.Additionally, in terms of redundancy, if one circuit crashes in a group,the entire system is not crashed. Systems are isolated so that they maybe replaced and maintained without affecting operations of othersystems.

In this non-limiting, exemplary instance illustrated, a first powersupply (about 48 volts) supplied power to a first set of circuits (e.g.,the X-, the Y-, and the Z-direction motive force mechanisms). A secondpower supply (about 24 volts) supplies power to a second set of circuits(e.g., computers, controllers, etc.). A third power supply (about 12volts) supplies power to a third set of circuits (e.g., the fans, etc.).As illustrated, first power supply and first set of circuits, secondpower supply and second set of circuits, and third power supply andthird set of circuits are isolated from one another. It should be notedthat optionally, and less preferred, a single power supply may be usedwith step-down transformers to supply power to various electricalequipment.

As further illustrated, the electrical circuits further include anUninterruptable Power Supply (UPS) system. UPS systems provideuninterruptable, clean auxiliary power in the case where main powersupplies are shut or cut-off, giving the floating tool sufficient timeto complete at least a part of the project before the entire system isshut-off. This is essential because the printers are slow and may be atthe end part of the project.

The circuit may further comprise drivers for stepper motors. The driversare general-purpose drivers and hence, use jumpers to set them up in adesired configuration. Micro, stepping is used to improve resolution ofprint (further granulated application of motive force to generate a morerefined, more granulated motion).

As further illustrated digital fabrication apparatus 100 furtherincludes to computer devices, a controller that includes firmwaremanagement and a Personal Computer (PC) system for computer monitorscreen 114. The present invention further includes two X-drive motors, 2Y-drive motors, and 4 Z-drive motors, including two additional motorsfor two filament drives.

In the non-limiting exemplary instance shown, digital fabricationapparatus 100 also includes beating system with its own plug-in power,with power passing through a Solid State Rely (SSR). Digital fabricationapparatus 100 further uses two fans for cooling the unit.

FIGS. 4A to 4H are non-limiting, exemplary illustrations of a floorplate assembly of the digital fabrication apparatus shown in FIGS. 1A to3D in accordance with one or more embodiments of the present invention.As illustrated, second section 106 of digital fabrication apparatus 100further includes a second horizontally oriented member 136 as afloor-plate assembly 156 that is mechanically connected to verticallyoriented frame members 134.

Floor-plate assembly 156 ultimately defines the X-coordinate and theY-coordinate of a work-surface 158 of a work-layer member 160 (FIG. 5F)a workpiece platform assembly 162 (FIG. 5A) and hence, the XY-plane ofwork-surface 158 with which a perpendicularly oriented Z-coordinate isassociated. Accordingly, the (X, Y, Z) position coordinates of moveablefabrication tool 118 is determined in relation to X, Y and Z coordinatesdefined by work-surface 158 of workpiece platform assembly 162,supported by floor plate 164 of floor plate assembly 156.

Floor-plate assembly 156 supports and stiffens workpiece platformassembly 162. As further detailed below, work-surface 158 of workpieceplatform assembly 162 defines the X- and the Y-coordinates of an XYplane of work-surface 158, with coordinate values (X=0, Y=0) defining acenter of work-surface 158. Accordingly, it is imperative that workpieceplatform assembly 162 remain substantially flat during operation anduse. As detailed below, floor-plate assembly 156 uses reinforcementmembers to assure that floor plate 164 (to which workpiece platformassembly 162 is secured) does not bend or wobble or move duringoperation but is stiff.

As illustrated, floor-plate assembly 156 is comprised of a first set ofreinforcement members 166 (FIG. 4E) that are mechanically connected(e.g., welded) to a second set of reinforcement members 168, which aremechanically connected (e.g., welded) to a bottom side 170 offloor-plate 164, forming floor-plate assembly 156. In other words, firstand second reinforcement members 166 and 168 provide a strong,truss-like structure, which ultimately define a constant XY-plane inrelation to moveable fabrication, tool 118.

First set of reinforcement members 166 extend longitudinally in a firstdirection, whereas second set of reinforcement members 168 extendlongitudinally in a second direction. First direction is at an angle inrelation to the second, direction—preferably, the first direction isperpendicular the second direction.

First set of reinforcement members 166 are comprised of cylindricaltubes that provide resistance against both torsion and angular forces.First set of reinforcement members 166 may be thought of as “torquetubes” that provide resistance against application of torque and angularforces (e.g., forces perpendicular to the longitudinal axis of the firstset of reinforcement members 166) to thereby maintain the floor plateflat and hence, ultimately, the XY-plane defined by work-surface 158.The first set of reinforcement members 166 absorbs applied torque orangular forces so that floor plate 164 continues to remain flat and notbend. In other words, they provide torsion and angular stiffness forfloor plate 164.

Second set of reinforcement members 168 are comprised of generallypolygonal cross-sectional profile that extends longitudinally, providingresistance against angular forces. In other words, they are extremelystiff vertically. Second set of reinforcement members 168 furtherinclude openings for passage of wiring, tubes, etc. Accordingly, firstand second reinforcement members 166 and 168 function to absorb torqueor other angular forces.

As best illustrated in FIGS. 3A and 4A to 4C, first and second distalends of the first set of reinforcement members 166 extend out of a firstset of vertically oriented frame members (oppositely positioned) and aremechanically connected (e.g., welded) to the first set of verticallyoriented frame members. First and second distal ends of the second setof reinforcement members 168 extend out of a second set of verticallyoriented frame members and are mechanically connected (e.g., welded) tothe second set of vertically oriented, frame members (oppositelypositioned).

As best illustrated in FIGS. 4D to 4H floor plate 164 is comprised offirst openings that define thermal expansion slots 172. As detailedbelow, workpiece platform assembly 162 must be heated for adhesion offilament onto work-surface 158 during fabrication of a workpiece.

Thermal expansion slots 172 are oriented and positioned to allow forin-plane thermal expansion of the workpiece platform assembly 162. Thisway, a center (X=0, Y=0) of the NY-plane of work-surface 158 ofworkpiece platform assembly 162 is maintained at a constant positionduring in-plane (or lateral) thermal expansion of the workpiece platformassembly 162. The location of the center position of the workpieceplatform assembly 162 must be constant while allowing expansions alongany in-plane (lateral) direction needed to counter repositioning orshifting of its center due to thermal expansion. Accordingly and asfurther detailed below, a minimum of four thermal expansion slots 172are needed to provide multi-directional lateral or in-plane expansion tomaintain the center of the workpiece at a constant position. This avoidsshifting of the center of the workpiece platform assembly 162 to oneside or the other due to thermal expansion.

Thermal expansion slots 172 comprise of a first pair of axially alignedthermal expansion slots that are oriented perpendicular a second pair ofaxially aligned thermal expansion slots. It should be noted that so longas the first pair of axially aligned thermal expansion slots areoriented perpendicular the second pair of axially aligned thermalexpansion slots, the slot-pairs may be position at any location on thefloor plate such as for example, near corners (e.g., diagonally oppositecorners) or along sides (as illustrated). In other words, the axes ofthe slot-pairs must cross at 90° degrees at center (X=0, Y=0) ofworkpiece platform assembly 162 (which is the same center as the floorplate 164 shown in FIG. 4D).

As indicated above, a first pair of axially aligned thermal expansionslots are positioned across floor plate 164, oriented parallel a definedX-coordinate of floor plate 164 (and ultimately X-coordinate ofwork-surface 158) that may be used to determine an X-coordinate positionof a moveable fabrication tool. A second pair of axially aligned thermalexpansion slots are positioned across the floor plate, oriented parallela defined Y-coordinate of the floor plate 164 (and ultimatelyY-coordinate of work-surface 158) that may be used to determine anY-coordinate position of moveable fabrication tool.

First pair of thermal expansion slots allow thermal expansion of theworkpiece platform 162 along an X-direction parallel X-coordinate, whilethe second pair of thermal expansion slots allow thermal expansion ofthe workpiece platform assembly along a Y-direction parallelY-coordinate.

First pair of thermal expansion slots are comprised of first and secondthermal expansion slots positioned at respective first and secondopposite peripheries of the floor plate 164, and have respective firstand second central longitudinal axis that are aligned. Second pair ofthermal expansion slots are comprised of third and fourth thermalexpansion slots positioned at respective third and fourth oppositeperiphery of the floor plate 164, and have respective third and fourthcentral longitudinal axis that are aligned. First and second oppositeperiphery define first and second sides of the floor plate 164, thirdand fourth opposite periphery define third and fourth sides of the floorplate. Alternatively, first and second opposite periphery define firstand second diagonal corners of floor plate 164, and the third and fourthopposite periphery define third and fourth diagonal corners of floorplate 164.

As illustrated, floor-plate 164 is generally polygonal (preferably, asquare) and includes a corner section 174 having a second opening 176for securing workpiece platform assembly 162 onto a top surface 178 offloor plate 164 of floor plate assembly 156 to prevent vertical movementof workpiece platform assembly 162 while enabling in-plane (or lateral)thermal expansion of workpiece platform assembly 162. That is, fastenerssecuring workpiece platform assembly 162 onto top surface 178 of floorplate 164 of floor plate assembly 156 through second openings 176prevent movement of workpiece platform assembly 162 parallel along framelongitudinal axis 130 while enabling in-plane thermal expansion ofworkpiece platform assembly 162.

The fasteners are enabled to move lateral (i.e., sway or tilt). Themovement is small and hence, the angular displacement is small (e.g.,smaller than micro-millimeters), but sufficient to accommodate thermalexpansion of the workpiece platform assembly 162 so to maintain, centerof work-surface 158 at (X=0, Y=0) location of floor plate 164.Non-limiting example of a fastener that may be used to tie workpieceplatform assembly 162 to floor plate 164 of floor plate assembly 156 isa shoulder bolt 182.

As is well known, shoulder bolts 182 have a cylindrical shoulder 184under the bolt head 186 that may serve as fulcrums and pivot (i.e.,tilt). In other words, well known shoulder bolts 182 in combination withretaining washers may be used with cylindrical shoulder 184 bolt head186 secured within second opening 176 of floor plate 164 from under side170 and moving (tilting due to expansion of workpiece platform assembly162) therein while the threading 188 of shoulder bolt 182 is screwedinto workpiece frame 190 (FIG. 5C) of workpiece platform assembly 162 toprevent vertical movement of workpiece platform assembly 162. This way,workpiece platform assembly 162 cannot be lifted, but may expandsideways.

FIG. 5H shows the CENTER throughbolt in the middle of each of the 4 legsof the frame; this bolt passes through the frame to engage with squareblock 214 which in effect becomes the threaded nut which tightensagainst the frame, and which in turn engages with the expansion slot inthe floor-plate; by doing so the two pairs of blocks allow expansion ofthe ‘printbed’ but constrain the center of the printbed not to moverelative to the floorplate.

FIG. 5H also shows how the diffuser plate 208 is supported within anarrow opening in the frame which effectively locates the plate alongall 4 edges of the periphery; the edge element 220 acts as a thermalelement to separate the edge of the diffuser plate 208 and the framebody 222

Additionally, stacked wave disc springs 192 may be also be used todistribute thermal expansion forces evenly on shoulder bolt components.Tightening shoulder bolt 182 compresses stacked wave disc spring 192against bottom surface 170 of floor plate 164 so that a certain load (apreload) is exerted on shoulder bolt 192. This enables fixing workpieceplatform assembly 162 vertically (by preloading it), but allows forlateral (in plane) thermal expansion due to stacked wave disc springs192.

As further illustrated, floor-plate 164 also includes third openings 194for securing a vertical guide rod 196 for the Z-direction motion ofmoveable fabrication tool 118 to thereby prevent “wobbling,” with thirdopenings 194 having fastener openings 198 to secure vertical guide rods196 via a linking adapter 200. At minimum two vertical guide rods 196may be used and positioned diagonally or, alternatively, as shown, fourvertical guide rods 196 used at each corner of digital fabricationapparatus 100.

As further illustrated, floor-plate 164 also includes fourth openings202 that are clearance holes for enabling passage of a threaded rodeassociated with Z-direction motive force mechanism, and a plurality offifth openings 204 (or general purpose openings) for passage of wiring.

FIGS. 5A to 5O are non-limiting, exemplary illustrations of a workpieceplatform assembly of the digital fabrication apparatus shown in FIGS. 1Ato 4H in accordance with one or more embodiments of the presentinvention. A workpiece (or an object) is fabricated on work-surface 158of a work-layer member 160 of workpiece platform assembly 162, withwork-surface 158 required to be heated for proper adhesion of filament.As, further detailed below, there are chain of constraints between thework-layer member 160 and floor plate 164 to ensure the constant centerpoint position (X=0, Y=0) of work-layer member 160 (which is the same asor coincides with the center of floor plate 164). Fasteners 206 thathold the work-layer member 160 in position connect with diffuser plate208, with diffuser plate 208 connected laterally with platform frame 190and the floor plate 164 (via third set of reinforcement members 210).

As detailed below, the entire workpiece platform assembly 162connections (from floor plate 164 to work-layer member 160) are toaccommodate and account for potential heat expansion of various layersof workpiece platform assembly 162 due to application of heat so thatthe position of the center of the workpiece platform assembly 162 isconstant in relation to floor plate 164 and that various layer thermalexpansions are tolerated while maintaining the structural integrity ofall layers. In other words, lateral thermal expansions are accounted forany member of workpiece platform assembly 162 that requires to bevertically secured so to maintain the center of the workpiece platformassembly 162 at a center (X=0, Y=0) coordinate values of floor pate 164.

Workpiece platform assembly 162 is secured onto floor-plate 164 (via theworkpiece platform assembly frame 190) to constrain workpiece platformassembly 162 from movement parallel along the frame longitudinal axis130 (vertical movement) while allowing in-plane (or lateral) thermalexpansion of the workpiece platform assembly 162. In other words,workpiece platform assembly 162 is secured onto floor-plate 164 toenable in-plane thermal expansion of workpiece platform assembly 162while preventing movement of the workpiece platform assembly 162parallel along frame longitudinal axis 130.

Workpiece platform assembly 162 is secured onto floor-plate by thermalexpansion couplers 212 (FIGS. 4G, 4H, and 5H to 5M), within thermalexpansion slots 172 of floor-plate 164 to reduce (or diffuse) adversethermal expansion effects on workpiece platform assembly 162 that mayresult in thermal stresses (generally laterally) on workpiece platformassembly 162.

Thermal expansion couplers 212 may comprise of a bolt/washercombinations secured within an thermal expansion member 214 (bestillustrated in FIGS. 4G, 4H, and 5H to 5M) that rests and moves within alarger thermal expansion slots 172 to enable the thermal expansionmember 214 to move “slide” within thermal expansion slots 172 as theworkpiece platform assembly 162 experiences thermal expansion due toapplication of heat. It should be noted that bolt/washer combinationalso secure workpiece platform assembly 162 onto a top surface of floorplate 164 of floor plate assembly 156 to prevent vertical movement ofthe workpiece platform assembly 162.

Alternatively, well known shoulder bolts 182 in combination withretaining washers may be also be used with the cylindrical shoulderunder the bolt-head secured within the expansion slot and moving(sliding due to expansion of workpiece platform assembly) therein whilethe threading of the shoulder bolt is screwed into the workpieceplatform assembly to prevent vertical movement of the platform. Thisway, the platform cannot be lifted, but may expand sideways.

Stacked wave disc springs may be also be used to distribute thermalexpansion forces evenly on shoulder bolts components. Tightening theshoulder bolt compresses the stacked wave disc spring against the bottomsurface of the floor plate so that a certain load is exerted on theshoulder bolt. This enables fixing the workpiece platform assemblyvertically, but allows for lateral (in plane) thermal expansion.

In general, workpiece platform assembly 162 is uniformly heated to adesired temperature generally commensurate with heating requirements foradhesion of filaments onto working-surface 158 of workpiece platformassembly 162. A combination of discrete heat sources 216 and a pluralityof heat diffuser layers provide uniform heating of working-surface 158of workpiece platform assembly 162 at the desired temperature.

Workpiece platform assembly 162 is comprised of discrete heat sources216 comprised of heating elements (also known as heating pads or heatsheets). Heating elements include an adhesive backing that fix theheating elements onto a bottom side of diffuser plate 208. It should benoted that floor plate 164 may further include a thermal insulator,which is connected to the top surface 170 of floor plate 164 to isolateheat emanating from heating elements 216.

The number of discrete heat sources 216 used for uniform heating ofworking-surface 158 of workpiece platform assembly 162 at the desiredtemperature is dictated by power rating and dimensions of discrete heatsources 216, and surface area of a diffuser plate 208 available withwhich, to associate discrete heat sources 216. Accordingly, the numberof discrete heat sources 216 used and the power rating selected toaccomplish the desired, uniform heating is a matter of geometry.

The uniform heat requirements are to have the maximum coverage whilemeeting the minimum heating requirements per unit area for work-surface158, Discrete heat sources 216 (e.g., heating elements or pads) aremanufactured at specific dimensions and power ratings. Therefore, thenumber, dimensions, and power rating of each discrete heat source 216used depends on the dimensions of diffuser plate 208 and the requireduniform heating of working-surface 158 of workpiece platform assembly162 (e.g., average Temp® per Unit Area).

Therefore, given the desired temperature requirements of filaments used,the next step is to determine the dimensions of working-surface 158 andthe desired temperature requirement per unit area that are generallycommensurate with the desired temperature for the filaments. Thereafter,determine the dimensions of the diffuser plate 208, which will determinethe number of discrete heat sources 216, power ratings, etc. based onthe available types that are needed. Accordingly, the illustrated numberand power ratings for the discrete heat sources 216 should not belimiting and may very well be varied. It should be noted that the lesserthe number of discrete heat sources 216 used, the simpler the controlsystem for delivering the appropriate heat. Therefore, it is preferredto use the least number of discrete heat sources 216 while maintainingthe required uniform heating.

As further illustrated, workpiece platform assembly 162 is comprised ofa platform frame 190 (similar to a picture frame) that confines multiplelayers of the workpiece platform assembly. Platform frame 190 hasmultiple, frame openings for securing workpiece platform assembly 162onto floor plate 164, with platform frame 190 in direct, mechanicalcontact with floor plate 164. Periphery edges 218 of diffuser plate 208of workpiece platform assembly 162 are inserted and secured withinlongitudinally extending channels 222 of platform frame 190, and coveredby an elastic thermal insulator 220 (similar to a shower glass beingsecured within an extruded aluminum shower glass frame by rubber).

Diffuser plate 208 is comprised of material that rapidly conducts tolaterally diffuse heat (non-limiting example of which may includealuminum) from discrete heat sources 216 and has a sufficient thicknessfor conduction of heat and to provide stiffness while enabling generallyuniform distribution of heat emanated from discrete heat sources. Thiseliminates potential “hot spots” on diffuser plate 208.

In addition to a diffuser plate 208 that facilitates uniform lateral(in-plane) distribution of heat, workpiece platform assembly 162 furtherincludes a thermally conductive pad 224 associated with a top surface ofdiffuser plate 208, which further facilitates uniform lateral (in-plane)distribution of heat. Further included is work-layer member 160 (e.g., aglass), which further facilitates in uniform distribution of heat.Work-layer member 160 includes working-surface 158, with work-layermember 160 positioned onto a top surface of the thermally conductive pad224. Accordingly, as heat is conducted towards working surface 158 ofwork-layer member 160, it continuously and uniformly diffuses to providea uniformly heated surface.

Diffuser plate 208 further includes third set of reinforcement members210 that are connected to a bottom surface of the diffuser plate 208,adjacent discrete heat sources 208, with third set of reinforcementmembers 210 connected between bottom surface of diffuser plate 208 andtop surface 178 of floor plate 164. Diffuser plate 208 is large 24″ by24″ and more and hence, reinforcement members 210 stiffen diffuser plate164 so that it does not change its flatness (especially due to potential“hot spots”).

Work-layer member 160 is comprised of high temperature material,non-limiting example of which may include borosilicate glass. Work-layermember 160 includes thermal expansion openings 226 for securingwork-layer member 160 onto diffuser plate 208 using thermal expansioncouplers 228. Thermal expansion openings 226 include a grommet 230,enabling for thermal expansion of the work-layer member 160 while beingconstrained from vertical movement. Grommets 230 provide elastomericseparating of opening 226 of work-layer member 160 and the shoulderbolts 182. This way, the mounting bolt 182 will not crack the work-layermember 160 during thermal expansion of member 160.

Work-layer member 160 is further comprised of sufficient thickness (atleast 9 mm or higher thickness) and includes curved periphery edges 230and curved vertices 232. Ideal shape for a uniform thermal expansion isa rounded circular disc where the center is equally distanced from, thecircumference or periphery edges (with no vertices) and hence, thecloser work-layer member is configured to a shape of a rounded circulardisc the better. A work-layer member with a polygonal periphery on theother hand, would have a center that is not equally distanced toperiphery edge and vertices of those edges. That is, the distance fromthe center to a periphery edge will be different from the distance fromthe center to a vertex associated with the periphery. Therefore, due tothe asymmetric distance, there might be a shift in the center of thework-layer member due to asymmetric thermal expansion. For example, avertex of a polygonal configured work-layer member may have a lowerthermal expansion rate due to its longer distance from the centercompared to a side (or periphery edge) that has a shorter distance fromthe center and hence, have a higher thermal expansion rate. Accordingly,work-layer member is shaped with curved periphery edges and curvedvertices, mimicking (as close as, possible) a disc structure. Ingeneral, workpiece frame 190 may be made larger to provide clearance forcurved edges 230 of work-layer member 160.

FIGS. 6A to 6P-4 are non-limiting, exemplary illustrations ofpositioning system of the digital fabrication apparatus shown in FIGS.1A to 5O in accordance with one or more embodiments of the presentinvention. As illustrated, digital fabrication apparatus 100 furtherincludes a positioning system for moving and positioning a movablefabrication tool 118 at a desired location within a three dimensionalspace 102.

The positioning system includes a movable positioning frame 234 thatsupports movable fabrication tool 118. Movable positioning frame 234 iscomprised of a flexible chassis 236 and a track mounting adapter 238that connects a track mounting assembly 240 to flexible chassis 236.

It should be noted that flexible chassis 236 is comprised of metal(about 6 mm thick aluminum). However, it may be flexed (even by hand) ator near its corners. Given the large movable positioning frame 234dimensions and the size of the X, Y, and Z motors used, the flexibilityof chassis 236 accommodate for variances in motor actuations, etc. whilemaintaining the movable positioning frame 234 parallel workpieceplatform assembly 162.

Flexible chassis 236 is comprised of sides that enclose an open area 242for free traverse of movable fabrication tool 118. Any one side ofchassis 236 has a width 244 that progressively decreases (or tapers)along a length 246 of the side from a middle portion of the side towardsa corner (or vertex) 248. Wider middle portion enables flexible chassis236 to be extremely stiff to thereby resist transverse (in-plane)bending. For example, it would be difficult to bend flexible chassis 236so that it forms into a trapezoid, Narrower corner portions 248 enablemaintaining flexibility at corners 248 of chassis 236 so that it is ableto bend at near corners 248 (out of plane motion) to compensate forvariations in Z-direction motion actuations from four Z-motors.

Flexible chassis 236 includes a first set of openings 250 positionedalong length 246 of the side for securing track mounting adapter 238,and includes a second sets of openings 252 positioned at corners 248that associate chassis 236 with the Z-direction motive force mechanisms(detailed below).

A first set of corner openings 254 of second set of openings 252 ofchassis 236 secure chassis 236 to a linking adapter 200, and a firstcorner opening 256 of first set of corner openings 254 function asreliefs to allow passage of a first component (i.e., guide rod 196) ofthe Z-direction motive force mechanisms. The number of guide rods 196may be two (which are diagonally positioned or four at each corner 248).

A second set of corner openings 258 of second set of openings 252 ofchassis 236 secure chassis 236 to a threaded nut assembly 260, which ispart of the Z-direction motive force mechanism. As a threaded rod 262 isrotated, threaded nut assembly 260 connected to chassis 236 moves theentire movable position frame 234 along Z-direction. A second corneropening 264 of second set of corner openings 258 of chassis 236 functionas reliefs to allow passage of a second component (i.e., threaded rod262) of the Z-direction motive force mechanisms.

Linking adapter 200 includes a first (or guide) opening 266 that isaligned with a first corner opening 256 that receive guide bar 196 thatconstrain movable positioning frame 234 from lateral (or in plane)motion while allowing or guiding movement along Z-direction. Linking,adapter 200 further includes a second (or Z-axis drive) opening 268 at adistal corner that is aligned with second corner opening 264 of thesecond set of openings 252 that function as reliefs to allow passage ofthreaded rod 262 of the Z-direction motive force mechanisms. As detailedbelow, as threaded rod 262 is rotated clockwise or counterclockwise,movable position frame 234 moves along the Z-direction, constrained byguide bar 196, which provides an in-plane or lateral stabilizing factor.

Linking adapter 200 further includes a main body 200 that includes thefirst (or guide) opening 266 with a swivel joint 270 inserted thereinfirst opening 266 and retained by atop retainer 272 from the top and abottom retainer 274 from the bottom (retainers 272 and 274 areidentical). Swivel joint 270 supports potential angular misalignment ofchassis 236 in relation to guide bar 196, i.e., potential out of planedeflections of chassis 236 perpendicular to guide bars 196. The lowerportion of the swivel joint 270 extends passed first corner opening 256of chassis 238 and retained by bottom retainer 274 to allow forpotential angular misalignments of chassis corners 248 in relation toguide bars 196. As illustrated, bottom retainer 274 has a curved outerperiphery that function as a relief for securing threaded nut assembly260 (which is part of the Z drive system).

It should be noted that chassis 236 (although made of metal or alloysthereof) is purposefully made to be “flexible” at the corners and hence,potential angular misalignment with relation to the guide bars 196exists during movement along Z-direction, which could potentially “bind”or “jam” the movement of the entire movable positioning frame 234 alongZ-axis. It is essential for chassis 234 to be flexible to toleratepotential variations or discrepancies between the Z-motors. Accordingly,the set up described maintains chassis 236 perpendicular to the guidebars 196, while guide bars 196 are perpendicular to workpiece platformassembly 162. This means that chassis 236 is maintained parallelworkpiece platform assembly 162.

Threaded nut assembly 260 is comprised of a threaded nut 276 with asupport adapter 278 that allows for threaded nut 276 to be connected toan underside of chassis 118 for lifting or lowering movable positioningframe 234. Instead of threaded nut 276, a threaded ball nut may also beused. This way, the balls of the threaded ball nut engage with, thethreads of threaded rod 262, which provides for a less friction and asmoother rotation of threaded rod 262. The threaded nut piece 276 isfastened onto support adapter 278 by a set of fasteners. FIGS. 6M-1 to6M-3 are non-limiting, exemplary illustrations showing acme threaded nutassembly 384 instead of assembly 260.

Track mounting adapter 238 is rigid member comprised of an “L” shapedbracket with a first section 280 having a first width 282 that is longerthan a second width 284 of a second section 286. In other words, trackmounting adapter 238 are “deep hang” in the vertical direction (wheninstalled) due to longer width 282 of first section 280. This providessufficient rigidity to carry the weight of track mount assembly 240 andgear rack 286, including all of the components that constitute the X andY direction motive force mechanisms such as motors, roller, etc.(detailed below). Track mounting adapter 238 must remain flat andstraight so to provide a rectilinear motion for the movable fabricationtool during use. This is the reason for fastening the gear rack 286 ontothe track, mounting adapter 238 (detailed below).

Track mounting adapter 238 includes a first set of openings 288 at afirst section 280 for mechanically connecting gear rack 286 to a firstside 290 of first section 280 of track mounting adapter 238. Trackmounting adapter includes a second set of openings 292 at second section286 for mechanically connecting track mounting adapter 238 to chassis236. Further included are access openings 294 for maintenance and set ofrollers, etc.

Gear rack 286 is a rigid member with a polygonal profile that extendslongitudinally along a longitudinal axis of gear rack 286. Gear rack 286includes cogs (teeth or gears of geared rack 286) positioned along aside of gear rack 286. Gear rack 286 is positioned on a third side 296of mounting bracket 298 and mechanically connected to track mountingadapter 238 via a set of fasteners. Gear rack 286 has a length that isshorter than a length of mounting bracket 298.

Track mounting assembly 240 is comprised of a track 300, a mountingbracket 298 and gear rack 286. Track 300 is connected to a first side302 of mounting bracket 298, with a second side 304 of mounting bracket298 connected to track, mounting adapter 238.

Track 286 is a smooth surfaced plastic with a polygonal profile(preferable rectangular) that extends longitudinally along alongitudinal axis of the track 286. Track 286 has distal end openingsthat secure track 286 on first side 302 of mounting bracket 298 by a setof fasteners 306.

It should be noted that the preferred position of gear rack is facingdownwards linear travel is guided preferentially by the track which isflat in contrast to gear wheel (pinion) which can be expected to haveminor deviations, especially once worn. Facing downwards, thearrangement of the gear rack is largely self-cleaning which preservesthe required engagement between the pinion and the gear rack.

Movable positioning frame 234 defines a plane at which movablefabrication tool 118 is positioned in relation to workpiece platformassembly 162. It should be noted that the plane at zero—(0) Z-axis (X=m,Y=n, Z=0) is defined by work-surface 158 of work-layer member 160 ofworkpiece platform assembly 162, which, in turn, is ultimately fixed toand set by floor plate assembly 156 and more particularly, floor plate164 (with its tab/slot connectivity with the vertical frame members 134)to which workpiece platform assembly 162 is secured.

FIGS. 7A to 7L are non-limiting, exemplary illustrations of X-directionmotive force mechanisms and Y-direction motive force mechanisms of thedigital fabrication apparatus shown in FIGS. 1A to 6P-4 in accordancewith one or more embodiments of the present invention. In thenon-limiting exemplary instance illustrated throughout all of thefigures and described, X-direction motive force mechanisms (shown inFIG. 7A) and the Y-direction motive force mechanisms (shown in FIG. 7B)are identical in every respect (and detail). Accordingly, a single setof drawings 7C to 7L are used to represent all details for both theX-direction motive force mechanisms (shown in FIG. 7A) and theY-direction motive force mechanisms (shown in FIG. 7B). It should benoted that optionally, the X- or the Y-direction motive force mechanismsmay be different and need not be identical.

An N-direction motive force mechanism and a Y-direction motive forcemechanism are mounted onto movable positioning frame 234 that movemovable fabrication tool 118 to desired location within an XY-planedefined by the Z position of movable positioning frame 234. As detailedbelow, Z-direction motive force mechanism moves movable positioningframe 234 along a Z-direction to a desired XY-plane.

X-direction motive force mechanism enables X-direction translationalmotion of movable fabrication tool 118, Y-direction motive forcemechanism enables Y-direction translational motion of movablefabrication tool 118, Z-direction motive force mechanism enablesZ-direction translational motion of movable fabrication tool 118.

X- and Y-direction motive force mechanisms are comprised of first Xmotor 308 and a second X-motor 308 driven (or powered) by X-motordriver, and a first Y-motor 308 and a second Y-motor 308 driven (orpowered) by a Y-motor driver. The drivers are located at lower section104 of digital fabrication apparatus 100 (FIGS. 3C and 3D).

Power to the first and second N-motors 308 are synchronously applied toenable synchronous rectilinear motion of movable fabrication tool 118 inthe X-direction within the X Y-plane Power to the first and secondY-motors 308 are synchronously applied to enable synchronous rectilinearmotion of movable fabrication tool 118 in the Y-direction within theXY-plane.

Use of two motors 308 associated with opposite distal ends of X-driveshaft reduces possibility of asymmetric drive of moveable fabricationtool 118 in X-direction. Use of two motors 308 associated with oppositedistal ends of Y-drive shaft reduces possibility of asymmetric drive ofmoveable fabrication tool 118 in Y-direction. That is, use of a singlemotor may move a first distal end of the drive shaft (X or Y driveshaft) while the second end lags. This may generate an in-plane (X-Yplane) rotations for moveable fabrication tool 118 rather than arectilinear motion. Accordingly, two motors are used and actuatedsynchronously.

Motors 308 are mounted onto preloading adapters 310, which, in turn, areassociated with track mounting assembly 240. The preloading adapters 310are comprised of a set of rollers 312 that engage track 300 while apinion 314 engages gear rack 286.

Preloading adapters 310 are further comprised of a compartment 314 thathouses a bearing 314. Preloading adapters 310 further include a firstset of openings 318 for securely mounting a motor 308, and a second setof openings 320 for mounting drag chains that may include power andsignal cabling for both the motors 308 and moveable fabrication tool118.

The X-direction motive force mechanism and the Y-direction motive forcemechanism are further comprised of a gear-shaft assembly 322 thatmoveably links first and second motors 308 of respective axis (the X orthe Y) while supporting movable fabrication tool 118 within the XY-planedefined by movable positioning frame 234. The gear-shaft assembly 322 iscomprised of a cylindrical link-shaft 324 (e.g., a linear motion shaft)having blind-holes 326 bored through partially along a centrallongitudinal axis of link-shaft 324, defining a first openings 328 forreceiving motor output shafts 330. The link-shaft 324 further includesan aligned second set of transversely oriented openings 332.

Gear-shaft assembly 322 further includes a pinion 314 (or engagementgear) that engages gear rack 286 to enable the rotational motion ofmotor output shaft 330 to be converted to a linear motion fortranslational motion of movable fabrication tool 118 (along X and Ydirections), Pinion 314 has a gear-hub 334 with a set of transverselyoriented openings 336.

Pinion 314 is interference fit (also known as press fit or friction fit)secured near an end 338 of link-shaft 324, while one or more set screws342 are used to secure (or trap or lock) motor output shaft 330 withinblind hole 326 through second set of opening 332 of link-shaft 324 andgear-hub openings 336. This enables link-shaft 324 to rotate in tandemwith motor output shaft 330. It should be noted that adhesives(including anaerobic adhesives) may also by used instead of interferencefit scheme to connect pinion 314 to link-shaft 324.

The free distal ends 340 of link-shaft 324 of gear-shaft assembly 322are positioned and rest within bearing 316 of preloading adapter 310.Link shaft 324 is long and heavy and therefore, the weight oflink-shafts 324 are carried by bearings 316.

As a side note, the link shaft 324 has three movements. It hasrotational movement, a translational movement, and potentially an axial(or lateral) movement (parallel along the central longitudinal axis ofthe link shaft 324.) As the X or Y set of preload adapters are moved,the entire X- or Y-direction motive force mechanism may move axially.This is because the rollers roll along the track with no constraints toforce them to have rectilinear motion. For example, as the X-directionmotive force mechanism is active, it will move the moveable fabricationtool along the X direction and position the moveable fabrication tool ata location with the proper X coordinate value. However, the motion ofthe moveable fabrication tool to a location with desired X value may“drag” or move the Y link-shaft of the Y-direction motive forcemechanism axially. In other words, potential exists that the rollers ofthe Y-direction motive force mechanism may move laterally whilepositioning the moveable fabrication tool at a desired X value whenX-direction motive force mechanism is active. However, this axialmovement does not impact the correct position of the moveablefabrication tool with respect to the X value. Therefore, although it maybe counterintuitive to allow or leave the rollers to “float” axially,their lateral or axial movement does not impact the final or stopposition of the moveable fabrication tool at the desired (X, Y, Z)position as each position value (X, Y, and Z) is arrived at separately.For example, a position with the correct X value of the desired locationis determined and moveable fabrication tool is moved to that location(regardless of any axial motion of Y-direction motive force mechanism)and the X direction motive force is stopped. Next, the Y value isdetermined and the Y mechanism moves moveable fabrication tool withoutaffecting the X since the X direction motive force is stopped (noactive). Accordingly, present invention provides a simple and costeffective scheme where added costly components to provide restrictionsin axial movement (such as using, costly V type rollers) is notnecessary. Accordingly, active motion in one coordinate (e.g., X) maytranslate into an axial passive motion in the other coordinately (e.g.,Y), with the axial passive motion having no impact or affect on theactive motion coordinate. In other words, longitudinal axis movement ofnon-active axis does not impact the correct positioning of the activeaxis.

As further side note and as importantly, all rollers 312 for bothX-direction motive force mechanism and the Y-direction motive forcemechanism are preloaded to give or provide an internal or additionalload independent of any working load when engaging track 300, which, inturn, preload the engagement of pinion 314 with gear rack 286. That is,the preloading allows the cogs of pinion 314 to mesh snuggly with thecogs of gear rack 286 to thereby reduce potential distortion ofoperations (e.g., reduce gear backlash 382, best shown in FIG. 7K) ofpinion 314 in relation to gear rack 286. FIG. 7L illustrated a preloadedpinion 314 and gear rack 286 with more intimately meshed cogs. Thesetranslate into a controlled motion and hence, correct positioning ofmoveable fabrication tool 118.

In FIG. 7K illustrates the incorrect engagement of pinion with rackgear. It should be noted that the gear shown rotating counterclockwiseto engage against the flank of the gear tooth so as to cause movement tothe left. Should the direction of rotation change to clockwise to causemovement to the right, the gap 382 I backlash between the teeth willresult in imprecision of translation of the input signal from thecontrol system to the correct location on the gear rack. Since thenature of 3D fabrication requires ongoing reversals, of direction andacceleration and deceleration along the X- or Y-axes, any backlash willresult in imprecision and therefore, reduced print quality.

As best illustrated in FIG. 7L, reduced backlash arrangement is achievedby preloading the arrangement through use of an elastic track whichprovides both an elastic load and also allows for minor deviations ingear engagement during, motion. It should be noted that whilecontrolling backlash is important, the use of a geared driveintrinsically limits backlash to a very small imprecision, by judiciousselection of gear parameters such as the gears and gears with finertooth spacing (pitch), most, imprecision due to backlash may becontrolled to an order of magnitude adequate to ensure acceptablequality.

As further detailed below, preloading the gears reduces the “clearance”or “dead zone” between cogs and hence, potential loss of motion,providing a more accurate positioning of moveable fabrication tool 118.However, the force applied for preloading must be sufficient that wouldsubstantially reduce backlash, but not jam the gears. It should be notedthat the present invention does not use gears for power transmission,but location. That is, the gears are not required to power a toolthrough a workpiece, but instead are merely used to position moveableprefabrication tool 118 at a desired location. Accordingly, gears arepreloaded for improved contact (meshing) of their respective cogswithout jamming. The cogs may “rub” against each other, which may slowthe speed at which the movable fabrication tool moves or even reduce thepower transfer due to added friction, but the moveable prefabricatedtool is light and does not require much power.

The present invention defines a load with its plain and ordinarymeaning, which is an external mechanical resistance against which amachine (the motor) acts. The present invention further defines the term“preload” with its plain and ordinary meaning, which is an intentionallyand purposefully added or addition load independent of the externalmechanical resistances against which a machine acts. In other words, inaddition to normal or inherent external mechanical resistances (orloads), the motors must also have sufficient power to overcome theintentionally given or imposed load (i.e., the preload).

The present invention further defines the term backlash with its plainand ordinary meaning, which is a clearance or lost motion in a mechanismcaused by gaps between the cogs of one gear and cogs of another gear. Inother words, a degrees of play between cogs—a mechanical form of a“deadband.” As best shown in FIG. 7L, backlash is the amount ofclearance between mated gear teeth. It can be seen when the direction ofmovement is reversed and the slack or lost motion is taken up before thereversal of motion is complete.

Well known threaded track rollers 312 with adjustable shoulder (alsoknown as eccentric track rollers) may be used to preloading theX-direction motive force mechanism and the Y-direction motive forcemechanism. The threaded track rollers 312 have shoulders that may beadjusted up or down to align to track 300, enabling uniform alignmentamong rollers 312 in a system. However, the present invention actuallyadjusts rollers 312 up or down to preload rollers 312 in relation totrack 300 so to preload pinion 314 in relation to gear rack 286.

As rollers 312 are preloaded onto track 300, rollers 312 roll over track300, which is a flat plastic strip with some elasticity. The elasticityeffectively functions as a spring and therefore, when the axle ofrollers 312 is oriented “downward” towards track 300, the contacting,surfaces of roller 312 contact (press against) the flat top surface ofplastic strip 300. This preloads pinion 314 in relation to gear rack286. That is, the elastic nature of plastic strip track 300 functioningas a “spring” pushes “up” against the rollers compression to “pull up”and preload pinion 314, pushed against in relation to gear rack 286. Inother words, the compression of rollers 312 against the plastic strip(track 300) and the elasticity of track 300 functioning as a “spring”against the roller compression provide a mechanical biasing scheme thatgenerate an increased holding or compression strength (hencefacilitating “preloading”) for the pinion and gear rack cogs. It shouldbe noted that optionally, reducing a diameter of the pitch circle of thepinion would further improve and reduces backlash and as importantly,further granulate the amount of travel (linear travel) thus improvingprecision.

FIGS. 8A to 8I are non-limiting, exemplary illustrations of a moveablefabrication tool of the digital fabrication apparatus shown in FIGS. 1Ato 7L in accordance with one or more embodiments of the presentinvention. As illustrated, the moveable fabrication tool 118 iscomprised of a first support module 344 and a second support module 346that are identical and that are cross-mounted.

First and the second support modules 344 and 346 are comprised of acylindrical interior 348 that extends longitudinally for receiving,link-shaft 324. First and the second support modules 344 and 346 furtherinclude first and second distal sections 350 and 352 and a cross-mountsection 354 that connects first and second distal sections 350 and 352.

Cross-mount section 354 has a lower profile compared to first and seconddistal sections 350 and 352 to reduce vertical span of link-shafts 324(for both X and Y) passing through respective first and the secondsupport modules 344 and 346. Cross mount section 354 forces link-shafts324 (for both X and Y) to be perpendicularly oriented. That is, sincelink-shafts 324 have both a rotational as well as translational motion,the cross-mount section forces link-shafts 324 to remain perpendicularduring operation. Cross-mount section 354 has fastener openings toenable secure connection of cross-mount sections 354 of first and thesecond support modules 344 and 346.

Distal portions of cylindrical interior 348 within first and seconddistal sections 350 and 352 include linear sleeve bearings 356 thatsupport link-shaft 324, with linear sleeve bearings 356circumferentially supported by O-rings 358. O-rings 358 are used tocorrectly compensate (by cushioning or deflections) for manufacturedtolerances (potential shaft misalignments) of link-shafts 324, the firstand the second support modules, and the rotational, translational, andaxial motion of the link-shafts. In other words, the linear sleevebearings 356 and the O-rings 358 maintain proper alignment or positionof link-shafts 324 during operation for correct positioning of themoveable fabrication tool 118. As further illustrated, linear sleevebearings 356 are retained within the first and second distal sections bya retaining cap 360 (a “dust” cap).

Mounted to exterior support section platforms 362 are filament driveadapters 364 for mounting a conventional filament drive. In general,filament drive adapters 364 may have configurations that would bestaccommodate largest number of different types of filament drivers 366.This way, users are not locked into using a specific brand or cartridgeof filament 368 for fabrication. In the non-limiting exemplary instance,the filament drive adapter 364 is configured as a “C”-like shape withfastener openings to connect filament drive 366 to the exterior supportsection platforms 362 and allow for securing of filament drive 366 ontofilament drive adapter 364. Other forms of filament drive adapter arecontemplated such as an “L” shape or others.

FIGS. 9A to 9N are non-limiting, exemplary illustrations of a top plateand Z-direction motive force mechanisms of the digital fabricationapparatus shown in FIGS. 1A to 8I in accordance with one or moreembodiments of the present invention. As illustrated, top-section 108includes a removable top closure (or the roof) 370 to provide acontrolled environment (in terms of temperature, humidity, etc.) withinmid-section 106 where the product is fabricated. The removable topclosure 370 enables full access to the top and middle sections forinitialization and setup of the workpiece platform assembly 162 andmoveable fabrication tool 118. It should be noted that completedfabricated piece may also be removed from the top (if necessary) afterremoving the top closure.

As illustrated, digital fabrication apparatus 100 includes a thirdhorizontally oriented member 136 as a top-plate 372. Top plate 372 iscomprised of a single piece polygonal ledge (preferably square to mimicfloor-plate 164 configuration) with openings that are aligned with floorplate 164 openings for guide bars 196 to ensure parallel orientation ofguide bars 196. This is further facilitated by the tab/slot connectivityscheme described above.

As further illustrated, filament 368 is wound on a spool 374 that issupported on an axel 376, which is connected to top plate 372. Spool 374is free to move or slide laterally along the longitudinal axis of axel376 as filament 368 is fed to moveable fabrication tool 118. There isalways sufficient slack of filament 368 that allows moveable fabricationtool 118 to move freely. It should be noted that instead of a stationaryaxel 376, the distal ends thereof may be associated with rollersaccommodated on tracks on the top plate. Further, two different spools374 (on the same axel 376) with two different types of filaments 368 maybe used to feed two different types of filament drivers 366.

As indicated above, the Z-direction motive force mechanism enablesZ-direction translational motion of movable fabrication tool 118.Z-direction motive force mechanism is comprised of four Z-motors 308 andone Z-motor driver (located with other X and Y drivers). The Z-motors308 are secured onto respective, four foundation-adapters 378 that areconnected to four corners of top surface of top plate 372 and torespective four axial load-bearing housings 380, which are connected tothe respective four foundation-adapters 378 from a bottom surface of topplate 372.

The four foundation-adapters 378 include raised openings 390 where theZ-motor rests and is secured, and a central opening 392 thataccommodates flexible coupler 394 (e.g., a helically flexible shaftcoupler). The raised openings 390 accommodate the upper portion of theflexible coupler 394 and also enable access to the clamping fastener 396of flexible coupler 394.

Four flexible couplers 394 connect motor output shaft 330 and the distalend 398 of threaded rods 262 together so that as the motor output shaft330 rotates, it rotates threaded rod 262, which, in turn, raises orlowers movable position frame 234. Helical flexible shaft couplers 394compensate for shaft misalignments such as angular, off-center, andaxial (it literally stretch along Z direction) by being flexible.

Axial load-bearing housing 380 carries the weight of movable positioningframe 234 and includes a thrust bearing 400 for supporting an axial loadcarried by the threaded rod 262 (one distal end of which is connected tothe threaded nut 276/384, which upholds movable position frame). Axialload-bearing housing 380 also includes a boss 402 that includes a setscrew that is used to attach boss 402 to threaded rod 262.

Boss 402 rests and provides, axial load on a top of the thrust bearing400, with a top piece of thrust bearing 400 rotating while a bottompiece of thrust bearing 400 is stationary and in full contact with aninterior bottom surface of axial load-bearing housing 380 to therebyenable axial, load bearing support while allowing rotation of thethreaded rod. As is well known, a thrust bearing is a particular type ofrotary bearing that is designed to support a predominately axial load.

To set a common Z-point within a single XY-plane for all Z-directionmotive force mechanisms, the nozzle of the moveable fabrication tool islowered to various points on the work-surface of the work-layer memberof the workpiece platform assembly, with gaps therebetween nozzle andsurface measured by a feeler gage. Thereafter, the chassis is adjustedby simply rotating the appropriate threaded rod of the specific Z motoris misaligned (the nozzle does not position within, the XY plane. Aswith XY motors, all signals to all Z-motors are synchronized tosynchronously rotate all four threaded rods and hence, move the moveablefabrication tool along the Z-direction perpendicular the XY plane of thework-surface.

Although the invention has been described in considerable detail inlanguage specific to structural features and or method acts, it is to beunderstood that the invention defined in the appended claims is, notnecessarily limited to the specific features or acts described. Rather,the specific features and acts are disclosed as exemplary preferredforms of implementing the claimed invention. Stated otherwise, it is tobe understood that the phraseology and terminology employed herein, aswell as the abstract, are for the purpose of description and should notbe regarded as limiting. Further, the specification is not confined tothe disclosed embodiments. Therefore, while exemplary illustrativeembodiments of the invention have been described, numerous variationsand alternative embodiments will occur to those skilled in the art. Forexample, work tool can be a router or similar machining tool; a laser orsimilar etch or marking tool; employ a digital device for measuring abody placed on the work surface for purposes of discovering the shape ofsuch body (reverse engineering)’ can be employed to simultaneouslyproduce multiple workpieces. Such variations and alternate embodimentsare contemplated, and can be made without departing from the spirit, andscope of the invention.

It should further be noted that throughout the entire disclosure, thelabels such as left, right, front, back, top, inside, outside, bottom,forward, reverse, clockwise, counter clockwise, up, down, or othersimilar terms such as upper, lower, aft, fore, vertical, horizontal,oblique, proximal, distal, parallel, perpendicular, transverse,longitudinal, etc. have been used for convenience purposes only and arenot intended to imply any particular fixed direction, orientation, orposition. Instead, they are used to reflect relative locations/positionsand/or directions/orientations between various portions of an object.

In addition, reference to “first,” “second,” “third.” and etc. membersthroughout the disclosure (and in particular, claims) is not used toshow a serial or numerical limitation but instead is used to distinguishor identify the various members of the group.

Further the terms “a” and “an” throughout the disclosure (and inparticular, claims) do not denote a limitation of quantity, but ratherdenote the presence of at least one of the referenced item.

In addition, any element in a claim that does not explicitly state“means for” performing a specified function, or “step for” performing, aspecific function, is not to be interpreted as a “means” or “step”clause as specified in 35 U.S.C. Section 112, Paragraph 6. Inparticular, the use of “step of,” “act of,” “operation of,” or“operational act of” in the claims herein is not intended to invoke theprovisions of 35 U.S.C. 112, Paragraph 6.

What is claimed is:
 1. A digital fabrication apparatus, comprising: aworkpiece platform assembly that is stationary and fixed to a frame ofthe digital fabrication apparatus; the workpiece platform assemblycomprising: a floor plate assembly; a diffuser plate; thermallyconductive pad; and work-layer member that includes a work surface uponwhich a workpiece is fabricated; the floor plate assembly is comprisedof: a floor plate with a bottom side and atop side; a first set ofreinforcement members that are mechanically connected to a second set ofreinforcement members, which are mechanically connected to the bottomside of the floor plate of the floor plate assembly; and a third set ofreinforcement members that are mechanically connected to the top side ofthe floor plate of the floor plate assembly; the floor plate, the firstset of reinforcement members, the second set of reinforcement members,and the third set of reinforcement members stiffen the workpieceplatform assembly and further, ultimately define a constant, fixed,XY-plane for the work-layer member in relation to a moveable fabricationtool.
 2. The digital fabrication apparatus as set forth in claim 1,wherein: the workpiece platform assembly is uniformly heated by acombination of a plurality of discrete heat sources and the heatdiffuser plate, providing uniform heating of working surface of workpiece platform assembly at a selected temperate.
 3. The digitalfabrication apparatus as set forth in claim 1, wherein: the pluralitydiscrete heat sources are comprised of a plurality of individual heatingelements that are fixed onto the heat diffuser plate; the heat diffuserplate rapidly conducts heat laterally from the plurality of individualheat elements and provides stiffness while enabling generally uniformdistribution of heat emanated from a plurality of individual heatelements to thereby eliminate potential hot-spots on the heat diffuserplate; wherein: the heat diffuser plate distributes heat to a largersurface area than a surface area of a heating element of the pluralityof individual heat elements.
 4. The digital fabrication apparatus as setforth in claim 3, wherein: the thermally conductive pad is associatedwith a top surface of the heat diffuser plate, which further facilitatesuniform lateral distribution of heat.
 5. A digital fabricationapparatus, comprising: positioning components for positioning a moveablefabrication tool along a Z-direction in relation to a defined XY-plane;the positioning components include: a moveable positioning frame having:a moveable chassis; a linking adapter connected to the chassis; thelinking adapter accommodating a guide bar that limits lateral movementof the moveable positioning frame, and accommodating a threaded rod of aZ-direction motive force mechanism that enable moveable positioningframe to move along a Z-direction by the Z-direction motive forcemechanism; and the moveable fabrication tool associated with thepositioning frame is moved along the Z-direction with four Z-directionmotive force mechanisms that operate together so that all corners of thepositioning frame are simultaneously moved together to maintain ahorizontal orientation of the positioning frame while moving alongZ-direction.
 6. A digital fabrication apparatus, comprising: positioningcomponents for positioning a moveable fabrication tool within anNY-plane; the positioning components include: a track mount assemblythat has: a rigid gear rack that includes cogs; and a track with asmooth surface; a preloading adapter: the preloading adapter iscomprised of: a set of rollers that engage the track; and a pinioncoupled with an axel and driven by one of an X direction motive forcemechanism and a Y direction motive force mechanism that engages the gearrack; the X direction motive force mechanism and the Y direction motiveforce mechanism, providing synchronous rectilinear motion of a movablefabrication tool within an NY-plane.
 7. The digital fabricationapparatus as set forth in claim 6, wherein: the track mount assembly iscomprised of a plurality of track mounting assemblies associated with amoveable positioning frame that, enable the moveable fabrication tool tomove along an NY-plane of the moveable positioning frame by theX-direction motive force mechanism and the Y-direction motive forcemechanism.
 8. The digital fabrication apparatus as set forth in claim 6,wherein: both the X-direction motive force mechanism and the Y-directionmotive force mechanism are preloaded in relation to the track mountingassembly to eliminate backlash.